Risk factors for Salmonella and hygiene indicators in the 10 largest Belgian pig slaughterhouses

A Review of Slaughter Practices and Their Effectiveness to Control Microbial - esp. Salmonella spp. - Contamination of Pig Carcasses

The BIOPIGEE project (part of the One Health European Joint Programme under Horizon 2020) aimed to identify relevant measures to effectively control Salmonella, and another zoonotic pathogen, hepatitis E virus (HEV) within the pig meat food chain. The aim of this study was to identify biosecurity measures or management practices that are relevant for limiting Salmonella and/or HEV occurrence and spread within pig slaughterhouses. This was with the final goal of compiling a list of biosecurity measures for different processes and operations along the slaughter line with evidence of their effectiveness. To achieve this, a literature review was conducted on studies estimating the effectiveness of measures applied in slaughterhouses to reduce the microbial contamination of pig carcasses. Results of this literature search are discussed and presented in summary tables that could be used as a source of information for the pig slaughter industry to further develop their guidelines on hygienic slaughter.

Microbiological Quality of Australian Beef, Sheep and Pork Carcases, Cuts and Offals

A one-year survey was undertaken of the microbiological quality of carcases and the derived primal cuts, manufacturing meat and offals at twelve Australian export establishments (six beef, three sheep/lamb and three pork). A total of 27,157 microbiological results for aerobic plate count (APC) and generic Escherichia coli were gathered, 15,155 from beef, 8405 from sheep and 3597 from pig establishments. The mean log10 APCs on beef, sheep and pig carcases were 0.84, 1.60 and 1.30 log10 cfu/cm2, respectively. For primals, the mean log10 APC was higher for beef but was similar for sheep and pork primals, with 'outside' cuts having higher counts. For manufacturing meat, the concentration was 2-3 log10 cfu/g, irrespective of species. The prevalence (%) of generic E. coli from beef, sheep and pork was 2.3, 28.4 and 5.4 on carcases; 7.0, 20.6 and 3.2 on primals; and 5.8, 33.6 and 6.1 on manufacturing meat, respectively. The mean log10 APCs of beef, sheep and pork offal were 3.23, 3.18 and 3.37 log10 cfu/g, with tripes and tongues having APCs 1-2 log10 units higher than organ offals. The results reflect improvements in total bacterial loadings compared with previous national baseline surveys.

Agar Contact Method as a Valuable Tool to Identify Slaughter Hygiene Deficiencies along the Slaughter Process by Longitudinally Sampling Pig Skin Surfaces

Examinations of total viable counts (TVCs) and Salmonella spp. on the skin of individual pigs during the slaughter process are useful to identify abattoir-specific risk factors for (cross-)contamination. At seven process stages (lairage to before chilling), pigs were bacteriologically investigated by repeatedly sampling the same animals using the agar contact method. The mean TVC of all pigs increased significantly at the first three tested process stages (mean count, after delivery: 5.70 log cfu/cm2, after showering: 6.27 log cfu/cm2, after stunning: 6.48 log cfu/cm2). Significant mean TVC reductions occurred after scalding/dehairing (mean count: 3.71 log cfu/cm2), after singeing/flaming (2.70 log cfu/cm2), and after evisceration (2.44 log cfu/cm2) compared with the respective preceding process stages. At the end of the slaughter line and before chilling, the mean TVC was 2.33 log cfu/cm2, showing that the slaughter process reduced contamination significantly. The slaughter process effectively reduced even very high levels of incoming TVCs, since at the individual animal level, at the end of the slaughter process, there was no difference in the TVCs of animals with initially high and initially low TVCs. Additionally, 12 Salmonella spp. isolates were recovered from 12 different pigs, but only until the stage after scalding/dehairing. Overall, the agar contact method used is valuable for detecting hygiene deficiencies at slaughter, and is animal-equitable, practical, and suitable for use on live animals.

Monitoring of Pig Slaughter Stages and Correlation in the Prevalence of Pathogens and Levels of Microorganisms That Indicate Microbiological Quality and Hygiene Using a Predictive Model

Pig production is relevant to the Brazilian economy. Different stages of the raising and slaughtering process influence the microbiological quality of pig products and by-products. Microbiological analysis and hazard analysis and critical control points (HACCPs) are tools for monitoring microbiological quality indicator microorganisms. The construction of predictive models can assist the process of monitoring the microbiological quality of pig products. This study aimed to map the slaughter stages and develop a model to predict the absence or presence of Salmonella based on the process variables (distance from the farm to the slaughterhouse and aerobic mesophilic) and analyze their influence on contamination indicator microorganisms. A total of 810 samples were collected at nine stages of the slaughter process (bleeding, scalding, dehairing, singeing, washing, evisceration, inspection, final washing, and chilling). The binary class predictive model was used as a microbiological quality predictor at the slaughter stages. Salmonella was identified at all process stages, with lower contamination levels at the scalding and chilling stages, whereas the highest levels were found at the dehairing and bleeding stages. The predictive model revealed an accuracy of about 85% for Salmonella being a tool to monitor the microbiological quality of pig slaughter.

Microbiological Quality of Pig Carcasses in a Slaughterhouse under Risk-Based Inspection System

Meat product inspection is one of the procedures adopted more than a century ago to guarantee food quality and safety for consumption. Due to technology and regulation advancement for farming and slaughtering pigs, a change in zoonotic profile attributed to pork has been identified. Thus, a global movement began to establish inspection parameters based on epidemiological risk profiles, culminating in the publication of a new regulation in Brazil in 2018. This normative instruction establishes that slaughterhouses under federal inspection must implement risk-based inspection until 2028. Changes in the inspection system can generate questions and objections on the part of customers and consumer markets. In order to assess microbiological contamination when adopting a risk-based inspection system, the occurrence of Salmonella spp. and the quantification of Enterobacteriaceae and mesophilic aerobic counts were compared in pig carcasses slaughtered under traditional and risk-based inspection systems. A statistical significance reduction was identified regarding the quantification of Enterobacteriaceae (log -0.18 to -1.61 CFU/cm²) and mesophilic aerobic counts (log 4.60 to 3.49 CFU/cm²). The occurrence of Salmonella spp. did not show a significant difference (4% to 5.3%). The results allowed us to conclude that adopting risk-based inspection systems improves food safety through Enterobacteriaceae and mesophilic aerobic counts reduction.

Singeing to improve visual aspect and microbiological quality of pig carcasses

ABSTRACT The proper operating conditions of the singeing machine on pig slaughterhouses to achieve good carcass quality are little reported. Thus, this study aimed to evaluate the effect of an automatic singeing machine on the quality of pig carcasses for better control in pork production. A two-factor (pressure and time) completely randomized design was used. The carcasses were subjected to four treatments using gas pressures of 0.6 and 0.8 kgf.cm-2 for 3.7 and 4.2 seconds of exposure to the flame. The carcasses were analyzed as for visual appearance, counts of Enterobacteriaceae and Escherichia coli, and temperature. Gas consumption was also assessed during the process. Carcasses subjected to 0.6 kgf.cm-2 for 4.2 s had a better visual appearance. Both pressure and time reduced the counts of Enterobacteriaceae and E. coli. Regarding gas consumption, exposure to the flame for 4.2 s consumed three times more gas than exposure for 3.7 s. Among the treatments tested, singeing using a pressure of 0.6 kgf.cm-2 for 4.2 s was sufficient to reduce microbial counts and improve visual appearance. This singeing standardization serves as a reference for slaughterhouses to produce pork with a visual appearance of better acceptability by consumers.

A quadruple protection procedure for resuming pig production in small-scale ASFV-positive farms in China

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African swine fever outbreak has caused serious economic losses in China. Pork supply in consequence faces huge demand.

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The small-scale farms in China are encountering difficulties in raising pigs.

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A comprehensive procedure was tested in 35 small pig farms that had been confirmed with African swine fever virus.

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During a one-year study, 100 percent of porkers and 98.8 percent of sows were healthy respectively.

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An effective biosafety procedure was developed for production of pigs in small-scale farms in China.

African swine fever (ASF) outbreak has caused serious economic losses in Asia since 2018. As ASF is a new emerging disease, many farmers hesitate to raise pigs before biosafety procedures were evaluated to be effective. To support small-scale farms in resuming pig production, a comprehensive procedure, called the quadruple protection procedure (QPP), was tested in 35 small farms which had been confirmed with African swine fever virus (ASFV). The QPP takes care of the farms' construction, environmental disinfection, regular immunization, and feed quality. Qualified daily management was supplemented as well. During a one-year survey four disinfectants and one piece of equipment were used in higher frequency. A 7- or 15-day empty period after the disinfection was suitable when it was combined with the rest of the protection measures from QPP. Totally 18,730 porkers and 3,006 sows were healthy by the end of the study with percentage of 100 and 98.8, respectively, indicating that QPP could protect pigs in small-scale farms from pathogens within China. This study developed an effective protective procedure system for small-scale farms to produce pigs under the risk of ASF outbreak.

Adding value to food chain information: using data on pig welfare and antimicrobial use on-farm to predict meat inspection outcomes

BACKGROUND

Using Food Chain Information data to objectively identify high-risk animals entering abattoirs can represent an important step forward towards improving on-farm animal welfare. We aimed to develop and evaluate the performance of classification models, using Gradient Boosting Machine algorithms that utilise accurate longitudinal on-farm data on pig health and welfare to predict condemnations, pluck lesions and low cold carcass weight at slaughter.

RESULTS

The accuracy of the models was assessed using the area under the receiver operating characteristics (ROC) curve (AUC). The AUC for the prediction models for pneumonia, dorsocaudal pleurisy, cranial pleurisy, pericarditis, partial and total condemnations, and low cold carcass weight varied from 0.54 for pneumonia and 0.67 for low cold carcass weight. For dorsocaudal pleurisy, ear lesions assessed on pigs aged 12 weeks and antimicrobial treatments (AMT) were the most important prediction variables. Similarly, the most important variable for the prediction of cranial pleurisy was the number of AMT. In the case of pericarditis, ear lesions assessed both at week 12 and 14 were the most important variables and accounted for 33% of the Bernoulli loss reduction. For predicting partial and total condemnations, the presence of hernias on week 18 and lameness on week 12 accounted for 27% and 14% of the Bernoulli loss reduction, respectively. Finally, AMT (37%) and ear lesions assessed on week 12 (15%) were the most important variables for predicting pigs with low cold carcass weight.

CONCLUSIONS

The findings from our study show that on farm assessments of animal-based welfare outcomes and information on antimicrobial treatments have a modest predictive power in relation to the different meat inspection outcomes assessed. New research following the same group of pigs longitudinally from a larger number of farms supplying different slaughterhouses is required to confirm that on farm assessments can add value to Food Chain Information reports.

Effect of gaseous ozone application during chilling on microbial and quality attributes of pig carcasses

Ozone application has been suggested as an additional measure to the slaughter animals under hygiene programs. In this study, we determined the efficacy of gaseous ozone applied to pig carcasses during chilling (16 h at 2-5°C). Forty carcasses were allocated to each treatment: control, without ozone application (T1) and 5 ppm gaseous ozone application (T2), divided in two 4-h periods. The carcasses were sampled before and after chilling. The average counts of total aerobic mesophilic (TAM) bacteria before chilling were not different (p = 0.55) between T1 and T2. In turn, after chilling, the ozone-treated carcasses had significantly reduced about 0.4 colony-forming units (CFU)/cm² of TAM counts (p < 0.001) than the control carcasses. No significant reduction was observed in the number of carcasses positive for Listeria sp. and Escherichia coli after gaseous ozone treatment; while a tendency (p = 0.08) of lower number of Salmonella positive carcasses in T2 was observed. Common macrorestriction (pulsed-field gel electrophoresis) patterns of S. enterica were observed in the carcasses before and after chilling. Pork samples from treated and untreated carcasses with ozone showed no lipid oxidation or altered color and pH. The results indicate that the gaseous ozone in the tested protocol is effective in reducing TAM populations, but not effective in decreasing the number of carcasses positive for E. coli and Listeria sp. Regarding Salmonella, the tendency of positive carcasses reduction may encourage further studies by testing other protocols of gaseous ozone application inside the chilling chamber.

Transmission of Bluetongue Virus Serotype 8 by Artificial Insemination with Frozen-Thawed Semen from Naturally Infected Bulls

Transmission of bluetongue (BT) virus serotype 8 (BTV-8) via artificial insemination of contaminated frozen semen from naturally infected bulls was investigated in two independent experiments. Healthy, BT negative heifers were hormonally synchronized and artificially inseminated at oestrus. In total, six groups of three heifers received semen from four batches derived from three bulls naturally infected with BTV-8. Each experiment included one control heifer that was not inseminated and that remained BT negative throughout. BTV viraemia and seroconversion were determined in 8 out of 18 inseminated heifers, and BTV was isolated from five of these animals. These eight heifers only displayed mild clinical signs of BT, if any at all, but six of them experienced pregnancy loss between weeks four and eight of gestation, and five of them became BT PCR and antibody positive. The other two infected heifers gave birth at term to two healthy and BT negative calves. The BT viral load varied among the semen batches used and this had a significant impact on the infection rate, the time of onset of viraemia post artificial insemination, and the gestational stage at which pregnancy loss occurred. These results, which confirm unusual features of BTV-8 infection, should not be extrapolated to infection with other BTV strains without thorough evaluation. This study also adds weight to the hypothesis that the re-emergence of BTV-8 in France in 2015 may be attributable to the use of contaminated bovine semen.

Identification of the Source for Salmonella Contamination of Carcasses in a Large Pig Slaughterhouse

To identify the major source of Salmonella contamination in a pig slaughterhouse, samples were collected from the clean and unclean area and Salmonella isolates were further typed. Carcasses entering the clean area showed a Salmonella contamination rate of 96.7% in the oral cavity and 55.0% in the rectum content samples. Evisceration seemed not to be critical as the contamination rate of the carcasses was similar before (16.7%) and after (18.3%) this slaughter step. In the unclean area, a limited number of oral cavity samples were positive after bleeding, while a dramatic increase of positives was observed after dehairing. Salmonella was detected in up to 0.01 mL of the recycled water collected from the dehairing machine. Genotyping of Salmonella isolates showed that similar pulsotypes were present in the oral cavity and recycled water. Based on these observations it can be concluded that the recycled water used in the dehairing machine was the major source for the carcass contamination in this slaughterhouse.

Critical Analysis of Pork QMRA Focusing on Slaughterhouses: Lessons from the Past and Future Trends

Foodborne microbial diseases have a significant impact on public health, leading to millions of human illnesses each year worldwide. Pork is one of the most consumed meat in Europe but may also be a major source of pathogens introduced all along the farm-to-fork chain. Several quantitative microbial risk assessment (QMRA) have been developed to assess human health risks associated with pork consumption and to evaluate the efficiency of different risk reduction strategies. The present critical analysis aims to review pork QMRA. An exhaustive search was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) methodology. It resulted in identification of a collection of 2489 papers including 42 on QMRA, after screening. Among them, a total of 29 studies focused on Salmonella spp. with clear concern on impacts at the slaughterhouse, modeling the spreading of contaminations and growth at critical stages along with potential reductions. Along with strict compliance with good hygiene practices, several potential risk mitigation pathways were highlighted for each slaughterhouse step. The slaughterhouse has a key role to play to ensure food safety of pork-based products but consideration of the whole farm-to-fork chain is necessary to enable better control of bacteria. This review provides an analysis of pork meat QMRA, to facilitate their reuse, and identify gaps to guide future research activities.

Antibody Responses to Salmonella in Pigs from Weaning Up to Marketing and Presence of Salmonella at Slaughter

Salmonella is estimated to be one of the leading causes of enteric illness worldwide. Human salmonellosis is most frequently related to contaminated food products, particularly those of animal origin, such as pork. Pigs are often asymptomatic carriers of Salmonella, highlighting the importance of identifying high-prevalence farms and effective detection methods. The objectives of this study were to investigate Salmonella antibody responses and their association with on-farm shedding and Salmonella isolation at slaughter. Fourteen groups of pigs from eight farrowing sources were followed from birth to slaughter (totaling 796 pigs). Information about farm management was collected through a questionnaire. Blood and fecal samples were collected four times at different stages of production, and palatine tonsils/submandibular lymph nodes were obtained at slaughter. Sera were tested for Salmonella antibodies by enzyme-linked immunosorbent assay, and fecal/tissue samples were cultured for Salmonella. Data were analyzed using a mixed-effect multivariable modeling method with farm, litter, and pig as random effects. Salmonella seropositivity rates were 20.3%, 5.8%, 15.9%, and 37.3% at weaning, at the end of nursery, at end of grower, and at end of finisher, respectively. Salmonella seropositivity and shedding increased with age (p < 0.05), and pigs shedding Salmonella were more likely to test seropositive (p = 0.02). Antibody response and shedding on-farm had no significant association with isolation of Salmonella from tissues harvested at slaughter. The variation in Salmonella seropositivity due to farm was 28.9% of total variation. These findings indicate that on-farm intervention may be a more effective approach to control Salmonella and to reduce the presence of Salmonella at slaughter. Additionally, the observation that some pigs in this study were Salmonella-negative throughout production and at slaughter is promising with regard to food safety, and studies are needed to explore the genotypes of those pigs.

Microbial Contamination Level Profiles Attributed to Contamination of Beef Carcasses, Personnel, and Equipment: Case of Small and Medium Enterprise Slaughterhouses

The microbial contamination level profiles (MCLPs) attributed to contamination of beef carcasses, personnel, and equipment in five Kenyan small and medium enterprise slaughterhouses were determined. Aerobic plate counts, Enterobacteriaceae, Staphylococcus, and Salmonella were used to determine contamination at four different slaughter stages, namely, dehiding, evisceration, splitting, and dispatch. Microbiological criteria of the four microorganisms were used to score contamination levels (CLs) as poor (0), poor to average (1), average (2), or good (3). MCLPs were further assigned to carcasses, personnel, and equipment at each stage by summing up the CL scores. The CL score attributed to aerobic plate count contamination was 2 or 3 for carcasses but 0 for personnel and equipment in almost all slaughterhouses. A score of 0 on carcasses was mostly attributed to Enterobacteriaceae at evisceration and to Salmonella at dehiding and evisceration. In addition, a score of 0 was mostly attributed to Staphylococcus contamination of personnel at dehiding. A score of 3 was attributed mostly to Enterobacteriaceae on hands at splitting, whereas a score of 2 was mostly attributed to the clothes at dehiding and evisceration. A CL score of 3 was mostly attributed to Enterobacteriaceae and Salmonella contamination of equipment at dehiding and splitting, respectively. Although CLs attributed to contamination of carcasses, personnel, and equipment ranged from 0 to 3, the maximum MCLP score of 9 was only attained in carcasses from two slaughterhouses at dehiding and from one slaughterhouse at dispatch. There is, therefore, a lot of room for small and medium enterprise slaughterhouses to improve their food safety objectives by improving food safety management systems at the points characterized by low CL scores.

Correlation between slaughter practices and the distribution of Salmonella and hygiene indicator bacteria on pig carcasses during slaughter

This study investigated the distribution of hygiene indicator bacteria and Salmonella on pig carcasses. Moreover, the relation between hygiene indicator counts and Salmonella presence as well as associations between specific slaughter practices and carcass contamination were determined for each carcass area. Seven Belgian pig slaughterhouses were visited three times to swab five randomly selected carcasses at nine different areas, after evisceration and trimming. Information about slaughter practices was collected using a questionaire. In all samples, the E. coli and Salmonella presence was analyzed and Enterobacteriaceae and total aerobic bacteria were quantified. Average total aerobic counts ranged from 3.1 (loin, pelvic duct, ham) to 4.4 log₁₀ CFU/cm² (foreleg). Median Enterobacteriaceae numbers varied between 0.4 (ham) an 1.8 log₁₀ CFU/cm² (foreleg). E. coli and Salmonella presence ranged from 15% (elbow) to 89% (foreleg) and 5% (elbow) to 38% (foreleg), respectively. Positive relations were found between hygiene indicator counts and Salmonella presence at the head, sternum, loin and throat. Several slaughter practices, such as splitting the head and incising tonsils, were associated with higher levels of hygiene indicator bacteria and Salmonella. These findings can be used to educate slaughterhouse personnel and estimate the public health risk involved in consumption of different pork cuts.

A Stochastic Model to Assess the Effect of Meat Inspection Practices on the Contamination of the Pig Carcasses

The objective of meat inspection is to promote animal and public health by preventing, detecting, and controlling hazards originating from animals. With the improvements of sanitary level in pig herds, the hazards profile has shifted and the inspection procedures no longer target major foodborne pathogens (i.e., not risk based). Additionally, carcass manipulations performed when searching for macroscopic lesions can lead to cross-contamination. We therefore developed a stochastic model to quantitatively describe cross-contamination when consecutive carcasses are submitted to classic inspection procedures. The microbial hazard used to illustrate the model was Salmonella, the data set was obtained from Brazilian slaughterhouses, and some simplifying assumptions were made. The model predicted that due to cross-contamination during inspection, the prevalence of contaminated carcass surfaces increased from 1.2% to 95.7%, whereas the mean contamination on contaminated surfaces decreased from 1 logCFU/cm² to -0.87 logCFU/cm², and the standard deviations decreased from 0.65 to 0.19. These results are explained by the fact that, due to carcass manipulations with hands, knives, and hooks, including the cutting of contaminated lymph nodes, Salmonella is transferred to previously uncontaminated carcasses, but in small quantities. These small quantities can easily go undetected during sampling. Sensitivity analyses gave insight into the model performance and showed that the touching and cutting of lymph nodes during inspection can be an important source of carcass contamination. The model can serve as a tool to support discussions on the modernization of pig carcass inspection.

A Rapid Systematic Review and Meta-Analysis of the Efficacy of Slaughter and Processing Interventions to Control Non-Typhoidal Salmonella in Beef and Pork

Pork is one of the major food sources of human salmonellosis worldwide, while beef products have been implicated in numerous foodborne outbreaks. As a result, effective interventions to reduce Salmonella contamination during beef and pork processing are of interest to both regulators and industry. We conducted a rapid systematic review and meta-analysis of literature investigating the efficacy of slaughter and processing interventions to control Salmonella in beef and pork. Review steps included: a comprehensive search strategy; relevance screening of abstracts; relevance confirmation of articles; data extraction; risk-of-bias assessment; meta-analysis (where appropriate); and a weight-of-evidence assessment. A total of 191 relevant experimental studies were identified. Two controlled trials indicated that hot water and steam treatments are effective at reducing the prevalence of Salmonella on beef carcasses (relative risk [RR] = 0.11, 95% confidence interval [CI]: 0.02, 0.58), while four trials found that pre-chill organic acid washes are effective at reducing Salmonella on pork carcasses (RR = 0.32, 95% CI: 0.13, 0.78), with high confidence in the estimates of effect. Four quasi-experimental studies found that post-exsanguination chemical washes were effective to reduce the prevalence of Salmonella on cattle hides, with low confidence in the specific estimate of effect; moderate confidence was found for the effect estimates of scalding (RR = 0.20, 95% CI: 0.14, 0.29) and singeing (RR = 0.34, 95% CI: 0.22, 0.52) of pork carcasses. The overall evidence supported enhanced reductions of Salmonella through a multiple-hurdle approach. In conclusion, various slaughter and processing interventions can contribute to reducing Salmonella on beef and pork carcasses, depending on the context of application; an appropriate combination should be selected, validated, and verified by establishment operators within their local conditions.

Effect of slaughterhouse and day of sample on the probability of a pig carcass being Salmonella-positive according to the Enterobacteriaceae count in the largest Brazilian pork production region

Sources of contamination of carcasses during slaughter include infected pigs as well as environmentally related sources. There are many microbial indicators that can be used in the processing of food to assess food hygiene and the safety of food processing. The presence of some microbial indicators can be viewed as a result of direct or indirect contamination of a food with fecal material. The presence of Enterobacteriaceae is often used as a hygiene indicator, as they are found both in the environment and in the intestine of warm-blooded animals. An association between Salmonella isolation and Enterobacteriaceae count (EC) on pre-chill carcasses has been described, however the impact of slaughterhouse and the day of sampling on the occurrence of Salmonella has not been previously investigated. To this end, mixed logistic regressions (MLRs) with random effects and fixed slopes were performed to assess the change in EC and its correlation with Salmonella occurrence using two data sets. The first describes the EC and Salmonella isolation in 60 pork carcasses in one slaughterhouse sampled at 11 different slaughter steps, including the carcass as a random effect. The second describes the EC and Salmonella isolation on 1150 pre-chill carcasses sampled in 13 slaughterhouses over 230 sampling days, and the model combined two random intercepts, slaughterhouse and date of sampling nested with slaughterhouse (day/slaughterhouse). Statistically significant associations (p<0.0001) between the log of the EC and Salmonella occurrence were found in all models. Nevertheless, although a strong association was found between Enterobacteriaceae and Salmonella contamination in pork carcasses, this association was not constant, given that there was a high variation in the probability of a carcass being positive for Salmonella according to the EC mainly between days of samples. The effect of the day of sampling on Salmonella prevalence was so large that the predictive value of the EC count for Salmonella isolation on a daily basis was compromised. It is possible that on some days batches with a high prevalence of Salmonella carriers shedding a high number of Salmonella were slaughtered. On these days, the potential for contamination/cross-contamination of carcasses will be so large that even hygienic slaughter, confirmed by the low EC on carcasses, will not be able to prevent the presence of Salmonella on some carcasses. The results of this study demonstrate that, despite the statistically significant association found, it may be difficult to predict when hygiene failure measured via EC actually indicates Salmonella contamination, and neither the inverse.

Modeling of Salmonella Contamination in the Pig Slaughterhouse

In this article we present a model for Salmonella contamination of pig carcasses in the slaughterhouse. This model forms part of a larger QMRA (quantitative microbial risk assessment) on Salmonella in slaughter and breeder pigs, which uses a generic model framework that can be parameterized for European member states, to describe the entire chain from farm-to-consumption and the resultant human illness. We focus on model construction, giving mathematical formulae to describe Salmonella concentrations on individual pigs and slaughter equipment at different stages of the slaughter process. Variability among individual pigs and over slaughterhouses is incorporated using statistical distributions, and simulated by Monte Carlo iteration. We present the results over the various slaughter stages and show that such a framework is especially suitable to investigate the effect of various interventions. In this article we present the results of the slaughterhouse module for two case study member states. The model outcome represents an increase in average prevalence of Salmonella contamination and Salmonella numbers at dehairing and a decrease of Salmonella numbers at scalding. These results show good agreement when compared to several other QMRAs and microbiological studies.

Salmonella control in live pigs and at slaughter

As European Union legislation sets reduction targets to lower the incidence of human salmonellosis, Member States are obliged to take effective measures to control Salmonella infection and contamination along the pig production chain. This review considers the most important control measures in the primary phase of pig production as well as during transport, lairage and along the slaughter line. Pig feed should be free of Salmonella, and contamination after feed processing must be prevented. Cleaning and disinfection procedures should be improved, although this can be complicated by the development of biofilms and the interaction between Salmonella and protozoa. Further research is required on the acid tolerance response of Salmonella strains regarding the use of organic acids in feed and/or drinking water. Vaccination of sows and piglets can be helpful but can interfere with current serosurveillance as no differentiation can yet be made between naturally infected and vaccinated animals. Fasting, transport and lairage conditions should be critically evaluated and improved. Slaughterhouses must avoid contamination and cross-contamination during all stages of the slaughter process. Scalding by steam and implementing a second singeing step after polishing are beneficial. Attention should be paid to the cleaning and disinfection procedures along the slaughter line. Carcass decontamination is a promising approach, but needs to be considered as a tool to add to good hygiene practices.

Modelling food safety and economic consequences of surveillance and control strategies for Salmonella in pigs and pork

Targets for maximum acceptable levels of Salmonella in pigs and pork are to be decided. A stochastic simulation model accounting for herd and abattoir information was used to evaluate food safety and economic consequences of different surveillance and control strategies, based among others on Danish surveillance data. An epidemiological module simulated the Salmonella carcass prevalence for different scenarios. Cost-effectiveness analysis was used to compare the costs of the different scenarios with their expected effectiveness. Herd interventions were not found sufficient to attain Salmonella carcass prevalence <1%. The cost-effectiveness of abattoir interventions changed with abattoir size. The most cost-effective strategy included the use of steam vacuum and steam ultrasound. Given uncertainty of the effect of steam vacuum and steam ultrasound, model results should be updated as more information becomes available. This framework contributes to informed decision-making for a more cost-effective surveillance and control of Salmonella in pigs and pork.

Assessing interventions by quantitative risk assessment tools to reduce the risk of human salmonellosis from fresh minced pork meat in Belgium

The risk of human salmonellosis through the consumption of minced pork meat in Belgium was assessed via a modular risk model covering pork meat production from lairage to human consumption. The main goal of the model was to give concrete options to reduce effectively the risk of human salmonellosis through the consumption of minced pork meat. These options (scenarios) were elaborated with reference to the international situation and the literature to give concrete and realistic possibilities for improving the microbiological quality of pork meat and to reduce the number of human salmonellosis cases per year in Belgium. The model estimates 15,376 cases of human salmonellosis per year in Belgium due to the consumption of minced pork meat. The results of the scenarios showed that the risk of human salmonellosis could be significantly reduced by efforts all along the pork meat production chain but also by efforts made by consumers. The responsibility of food business operators for the pork meat production chain is high in relation to the microbiological quality of meat delivery, especially at the slaughterhouse. Consumers also need to be aware of good hygiene practices during preparation of the meat at home. Cross-contamination with raw food can be avoided by changing the habits and the behavior of the household cook. The results of these scenarios would be useful for the food business operators involved in the pork meat chain and for public health authorities.

Development of a quantitative microbial risk assessment for human salmonellosis through household consumption of fresh minced pork meat in Belgium

A quantitative microbial risk assessment (QMRA) according to the Codex Alimentarius Principles is conducted to evaluate the risk of human salmonellosis through household consumption of fresh minced pork meat in Belgium. The quantitative exposure assessment is carried out by building a modular risk model, called the METZOON-model, which covers the pork production from farm to fork. In the METZOON-model, the food production pathway is split up in six consecutive modules: (1) primary production, (2) transport and lairage, (3) slaughterhouse, (4) postprocessing, (5) distribution and storage, and (6) preparation and consumption. All the modules are developed to resemble as closely as possible the Belgian situation, making use of the available national data. Several statistical refinements and improved modeling techniques are proposed. The model produces highly realistic results. The baseline predicted number of annual salmonellosis cases is 20,513 (SD 9061.45). The risk is estimated higher for the susceptible population (estimate 4.713 x 10(-5); SD 1.466 x 10(-5)) compared to the normal population (estimate 7.704 x 10(-6); SD 5.414 x 10(-6)) and is mainly due to undercooking and to a smaller extent to cross-contamination in the kitchen via cook's hands.

Factors associated with Salmonella prevalence on pork carcasses in very small abattoirs in Wisconsin

The U.S. Department of Agriculture has expressed concern over Salmonella prevalence on pork carcasses. Our objectives were to survey the prevalence of Salmonella on pork carcasses in very small Wisconsin abattoirs, and identify processing conditions and indicator bacteria levels associated with reduced Salmonella prevalence. During April to July 2007, sponge samples were obtained from 181 pork carcasses at 10 Wisconsin abattoirs before carcass washing (carcass half A), and after washing and chilling and before fabrication (carcass half B). Each sample was categorized by whether the carcass was skinned, by wash-water temperature (7 to 43 degrees C), and the duration (1 or 2 days), temperature, and percent relative humidity of chilling. Sponge samples were analyzed qualitatively for Salmonella and quantitatively for Escherichia coli, coliforms, Enterobacteriaceae, and aerobic plate count (APC). Salmonella prevalences on skinned and unskinned prewash carcasses were 11.7 and 8.3%, respectively. Corresponding values for chilled carcasses were 32.0 and 19.5% for 1-day chilled carcasses, and 11.4 and 14.7% for 2-day chilled carcasses. Lower Salmonella prevalence on prewash carcasses was significantly related to lower prewash carcass APC levels (odds ratio = 7.8 per change of 1.0 log CFU/cm2), while lower Salmonella prevalence on chilled carcasses was significantly related to 2-day chilling (odds ratio = 5.2), and chilled-carcass levels of coliforms, Enterobacteriaceae, and APC (odds ratio = 1.5 to 1.9 per change of 1.0 log CFU/cm2). Salmonella prevalence on chilled pork carcasses in very small Wisconsin plants could be reduced by chilling carcasses 2 days before fabrication and improving carcass-handling hygiene.